Hi thank you for your question hope this helps.
There have been lots of problems with the grand cherokee signals Intimately working then not.
A lot or the problems can be teased to the turn signal switch / multifunction switch or the hazard light switch, it can also be the turn signals flasher.
But lets start with your sometimes what is happening with your turn signals?
Vary common problem this is the signal switch / multifunction switch that has failed.
There is a trick you can try till you get around to replacing the switch.
With the turn signal on "like when you are making turn" turn on the hazard for one blink.
The turn signals will work for a short time.
In some rare cases this can traced to a faulty turn signal flasher i would change the flasher first just because it is the essayer of the two to change. and if you are replacing the turn signal switch it is a good idea to replace the flasher.
The flasher is located in junction block (fuse panel) Front seating area, driver side, under dash, The factory flasher is light blue.
Simply pull out the old one and push in the new one.
Removal & Installation
Hope this helps